In a statement, his office said he had also suspended his close aide, David Babachir Lawal, pending an investigation into contracts awarded to deal with the humanitarian crisis in the north-east. The region has been hit by an insurgency by militant Islamist group Boko Haram.

A three-member panel, led by Vice-President Yemi Osinbajo, will investigate both cases, Mr Buhari's office added.

Apart from US notes worth $43.4m, the Economic and Financial Crimes Commission (EFCC) found nearly £27,800 and some 23m naira ($75,000) at the empty flat in Lagos's affluent Ikoyi suburb.

The National Intelligence Agency (NIA), which led by Mr Oke, had laid claim to the money, Mr Buhari's office said.